Various processes have been proposed for the disproportionation of chlorosilanes to obtain silanes from which silicon of high purity can be produced. The known processes present a number of disadvantages from the standpoint of reaction rate, temperature, contamination, corrosion resistance and economy.
The known process of employing an ion exchange resin containing tertiary amino or quaternary ammonium groups as disclosed by Litteral in U.S. Pat. No. 4,113,845 uses a toluene process to dehydrate the resin bed. The copolymerization of a monounsaturated hydrocarbon, such as styrene, which is a monomer not containing any basic functional group, and a polyunsaturated hydrocarbon, such as divinylbenzene, and introducing as a basic functional group a tertiary amino or quaternary ammonium group which is bonded to the matrix through carbon, provide a basic ion exchange resin. The tertiary amino or quaternary ammonium group bonded to the aromatic nucleus through carbon can be eliminated from the aromatic nucleus as a small molecule such as trimethylamine. The elimination reaction can be promoted by heating and by catalytic action of silicon tetrachloride, trichlorosilane, dichlorosilane, or monochlorosilane. The formation of the small molecule gives always the contamination to the disproportionated products from the catalyst used. The separation of the functional group restricts the use of the catalyst to temperatures below 80.degree. C. and the maximum yield to 8 mole percent of dichlorosilane in the reaction process. Additionally, the use of a safer and more economical means for drying the resin bed which requires temperature of greater than 50.degree.-80.degree. C. results in separation of the functional group of the catalyst which renders the catalyst ineffective.